Research in the last few decades has led to a plethora of confusing assertions concerning the relationship of diet and cancer. Except in a few cases, the scientific validity of these concepts has neither been critically examined nor communicated to the public. Furthermore, there is no clear understanding of the priorities and directions for future research. Therefore, it is proposed that the National Academy of Sciences critically assess the existing data concerning the possible relationship of dietary components (nutrients and toxic contaminants), and nutritional factors to the incidence of human cancer. A committee of approximately fourteen members will be formed to: conduct a comprehensive review of the state of knowledge in this area; identify and summarize pertinent information that can be communicated to the scientific community and to the public; and identify gaps in the data base and develop components, nutritional factors, and cancer.